Add SkColorSpacePrimaries to help with making D50 matrices

src/core/SkColorSpace_Base.h

Index: src/core/SkColorSpace_Base.h
diff --git a/src/core/SkColorSpace_Base.h b/src/core/SkColorSpace_Base.h
index 38e0ba002682e3deb82b93cdc41effbb7a4d61b6..65930946c5aa821048757bcf869cafa8a82fbcf7 100644
--- a/src/core/SkColorSpace_Base.h
+++ b/src/core/SkColorSpace_Base.h
@@ -34,18 +34,7 @@ struct SkGammas : SkRefCnt {
         }
     };
 
-    // Contains the parameters for a parametric curve.
-    struct Params {
-        //     Y = (aX + b)^g + c  for X >= d
-        //     Y = eX + f          otherwise
-        float                    fG;
-        float                    fA;
-        float                    fB;
-        float                    fC;
-        float                    fD;
-        float                    fE;
-        float                    fF;
-    };
+    // TODO: A bunch of name changes so the world still compiles.
 
     // Contains the actual gamma curve information.  Should be interpreted
     // based on the type of the gamma curve.